The seeds of sesame has been used as a food stuff in the world since several thousand years ago, and their nutritional values have been recognized for many years. In addition, scientific studies have been carried out for their functional utilities, and as a result, for sesame lignans which are ingrients particularly contained in the seeds, interesting unique functionalities have been found.
As sesame lignans there are sesamin, sesamolin, sesaminol and the like. Sesaminol is present in the seeds mainly as glygoside, and also can be produced from sesamolin.
The active oxygen produced in the body of human is toxic for human if its amount is in exess, and for instance, it is said that it may cause ageing, cancer, diabetes, Alzheimer disease and the like. To inhibit the active oxygen, it is necessary to take materials having antioxidative action and therefore the investigation searching for effective antioxidation materials has been effected.
The sesame lignans have this antioxidative effect, and especially sesaminol has the strongest effect and also sesamin has the similar effect.
The following has been known for sesamin. Sesamin can significantly inhibit the enzyme linked to the production of arachidonic acid (as the starting material linolic acid is used) which is a precursor of prostaglandins having physiological activites such as contraction and relaxation of smooth muscle, aggregation of blood platelet, inflammation etc. Further, sesamin prevents effectively liver disorder because it decomposes effectively ethanol in the liver. In addition, sesamin controls the increase of cholesterol while it decreases LDL cholesterol and is also effective for the lowering of blood pressure.
From the above, it is especially useful to obtain sesamin, sesaminol and sesamolin which can also produce sesaminol by transition from sesame seeds.
As the process of obtaining sesame oil from sesame seeds, mainly press process and extraction process with organic solvent (hexane is used)can be used. In the press process, the product still contains the oil whereas in the extraction process it may be difficult to eliminate completely the organic solvent residue in the extract.
The sesame lignans are contained in the sesame oil in an amount of about 1%. Generally it is very difficult to isolate a trace amount of oil-soluble active materials present in the oil. Thus, the previous processes to isolate the sesame lignans such as sesamin are, for example, one in which sesamin can be obtained from scum of byproduct recovered by the refinement of crude pressed sesame oil, and a process of obtaining sesame lignans by carrying out the molecular distillation of the scum has been proposed (JP10-120695A). In this process, the amount of the scum used as the starting material is limited, and the cost of the installation is high, and the treatment period is longer, and it is difficult to obtain the product in greater amount in view of the nature of the production plant. During the refining step of the starting crude press sesame oil, significant amount of sesamin is epimerized to episesamin. The physiological properties of the episesamin such as the inhibition activity of the enzyme linked to the production of arachidonic acid is lowered approximately half as much as those of sesamin. In this process, sesamolin is seldom isolated and the isolation of sesaminol is also difficult.
The inventors have previously found the process of treating sesame under supercritical extraction conditions to obtain sesame lilgnans and sesame flavor from sesame seeds. As a result, different from the prior processes, sesame lignans contained in the sesame seeds could be recovered in higher purity and yield, and also the flavors contained in the sesame seeds could be obtained.
In the previous process which the inventors had effected, the sesame lignans and flavors could be obtained in higher purity and yield comparing with the prior art processes, but as the starting material is sesame seeds, it is not convenient to recover the product sesame lignans and the production cost is much higher. In addition, since the product obtained in this process contains oily sesame lignans, it is necessary to use special treatment to obtain the sesame lignans in higher concentration or in solid state.